docs: add module documentation in AsciiDoc with PlantUML diagrams

Generated by per-group subagents covering all 52 modules across:
core (18), infrastructure (10), apps (5), interfaces (3),
plugins (7), testing (9)

Documentation format:
- AsciiDoc (.adoc) files in docs/modules/<group>/
- PlantUML (.puml) files in docs/diagrams/
- .adoc files reference diagrams via include:: directives

Each doc covers: purpose, responsibilities, non-responsibilities,
key types, event flow, integration points, invariants, PlantUML
diagram, known issues, and open questions.

docs/diagrams/infra-persistence.puml

@@ -0,0 +1,16 @@
+@startuml
+!theme plain
+package "infra-persistence" {
+  class InMemoryEventStore
+  class SqliteEventStore
+  class LiveArtifactRepository
+  class JDBCHelper
+}
+interface EventStore <<core:events>>
+ArtifactRepository <<core:artifacts>>
+EventStore <|.. InMemoryEventStore
+EventStore <|.. SqliteEventStore
+ArtifactRepository <|.. LiveArtifactRepository
+LiveArtifactRepository --> EventStore : subscribes
+SqliteEventStore --> JDBCHelper : uses
+@enduml